1. Field of the Invention
The present invention relates to a method for pressing a liquid extract from material to be pressed, in which a screw press conveys the material to be pressed along a pressing route and applies pressure to it, and in which the material to be pressed is treated with at least one extracting agent, which is removed from the pressed material together with the extract.
In addition, the invention relates to a device for pressing a liquid extract from a material, which device is designed as a screw press which has a worm that is movably guided in a cylinder wall and which is connected to at least one feeding device for an extracting agent and to at least one collecting device for the extract.
2. Description of the Related Art
Methods and devices of these types are used, for example, to press oil from oilseeds. It is already well known that the pressing process can be assisted by mixing the material to be pressed with a large excess of supercritical carbon dioxide and dissolving the oily extract in the supercritical carbon dioxide at very high pressures. In this connection, the supercritical state describes a physical state of matter in transition from the gaseous to the liquid phase of the carbon dioxide. After being removed from the press, the extract dissolved in the supercritical carbon dioxide is recovered in pure form by vaporization of the carbon dioxide. The vaporized carbon dioxide is either released into the atmosphere or recompressed and reused.
The production and handling of the supercritical carbon dioxide and the necessary equipment expense for handling the considerable amounts of this extracting agent result in expenses that are too high for many applications.